44 nil-: vhemistry a\j> I'livsics of the cell 



THE NUCLEUS 2* 



Although the luieleus i)reseiits morphologically a sharp isolation 

 from the cytoplasm, and displays eciually sharp tinctorial ditt'erences, 

 it is probable that chemically the ditt'erences between nucleus and cy- 

 toplasm are quantitative rather than qualitative. The characteristic 

 affinit}' of certain elements of the nucleus for basic stains depends 

 upon the presence in the nucleus of nucleoproteins in large proportion, 

 and to a limited degree nucleoproteins are characteristic of nuclei. 

 Their affinity for basic dyes depends upon the nucleic acid radical.-*'* 

 For exami)le, the heads of spermatozoa contain nucleic acid bound to 

 simple proteins in such a way that it readily forms a salt or salt-like 

 combination with basic dyes, and so the sperm heads appear intensely 

 stained by alum-hematoxylin, etc. Ordinary chromatin threads of 

 nuclei appear to contain somewhat more firmly bound protein in their 

 nucleoprotein molecules, and hence stain less intensely than do the 

 spermatozoa heads, except when in karyokinesis, when the chromatin 

 nucleoprotein seems to approach that of the spermatozoa in avidity for 

 basic dyes. We also have nucleoproteins with the nucleic acid so thor- 

 oughly saturated by protein that they do not stain at all by basic dyes, 

 and these seem to exist principally in the cytoplasm, and also to form 

 the ground-substance of the nuclei, occupying the spaces between the 

 chromatin particles (this achromatic substance of the nuclei is called 

 linin or plastin by some cytologists). Besides the chromatin and the 

 nucleoli, there is a peculiar chromatophile substance, suspended in the 

 liner part of the nuclear structure in the same manner as the chromatin 

 itself is in the coarser portions ; this was called lanthanin by Heiden- 

 hain,-^ and is probably similar to the substances also described as para- 

 ehromatin and paraUnin. Undoubtedly the other forais of proteins 

 found in the cell, such as globulin, albumin, and nucleoalbumin, exist 

 both in the nucleoplasm and in the cytoplasm, the essential difference 

 being that the proportion of nucleoprotein is much greater in the nu- 

 cleus. As nucleoproteins are little affected by peptic digestion, it is 

 possible to isolate nuclear elements, especially the chromatin, for analy- 

 tic purposes, and it has been demonstrated by this means also that 

 nuclein is the chief constituent of the staining elements. The distribu- 

 tion in the nucleus, of the other primary constituents of the cyto- 

 plasm, such as lecithin, cholesterol, and inorganic salts has not yet been 

 worked out, except that IMacallum -*' has found that nuclei contain no 

 chloi-ide, as indicated by their not staining with silver nitrate, and 



2^ Karlicr litcraturo by Alhroclit, "Pathologio der Zcllc." Luliarscli-Ostortafr. 

 Erjrcl). <lcr allff. Pathol., I'snO (0), 1000: see also Kossel, Miiufli. med. Wocli.. 1011 

 (58), 05. 



:;-iH Tferwerden (Arch. Zcllforscli.. l!ll:! (]'.)). -l.'il ) found lliat llie liasopliilic 

 firanules are disintc^rralcd spccidcallv l)y mudcase. siijiiiortiiij: 1hi> view that they 

 are mi(deic acid com pounds. 



■■^■- Fcstsdir. f. K.illikcr. 1802, p. 128. 



-'•i I'rocecdinL's of Ihc K'oval Societv. IHO.-) (Tfi). 217. 



